Commutators of rotary electric machines



COMMUTATORS OF ROTARY ELECTRIC MACHINES FiG.1- 3

Filed June 9, 1966 Sheet I of 2 2 FI G.2 9v

1+ 2 3 5 6 FIG.3 1 ,X,

June 17, 1969 J. DEMERCIERE COMMUTATORS OF ROTARY ELECTRIC MACHINES 2 of2 I Sheet Filed June 9, 1966 FiG.4.

United States Patent Int. (:1. H01r 39/04 US. Cl. 310-236 6 ClaimsABSTRACT OF THE DISCLOSURE A communtator for rotary electrical machineshaving a sleeve on which are mounted a plurality of similar radialconductive elongated bars with interposed insulating plates separatingsuccessive bars. Each bar has a notch in its inner edge, which extendsat least in part within the body of the bar to form a tongue thereinalong the edge. At one radial end of the bar is a further notch and atthe other end is a radial outwardly directed extension and a lateralprojection, the latter having an outline matching that of the furthernotch and being disposed at the same level thereof. An insulating bodyis secured to the sleeve and fills the notches and encloses theprojections of the bars, there being rings imbedded in the insulatingbody and fitted in corresponding notches of the different bars andextending around the lateral projections on the different bars.

The bars or strips of molded and reinforced commutators in motors andthe like rotary electric machines are generally fitted round a centralsleeve by means of metal rings housed in pairs in one or more notcheshaving a T-shaped outline and which are provided in the inner centralsection of each bar, the insulation between the bars and their carrierrings being obtained by molded or injected insulating material.

The collar provided at one end of certain commutators for the electricconnection between the windings and the bars produces in registry withthe location of the collar a considerable increase in the centrifugalforce, which has a tendency to tear the bars'out of their housings.

In order to eliminate this drawback, the bars have been provided at saidend with a terminal notch adapted to be engaged b a further ring.

However, the reduction in the thickness of the metal between saidterminal notch and the above mentioned T-shaped notch reducesconsiderably the clamping action on each bar so that the increase in therotary speed allowed by said further ring is quite inconsiderable.

My invention has for its object to remove this drawback and, to thisend, it improves the commutators of the above-mentioned type for allrotary electric machines. According to my invention, each bar includesin its radially inner surface one or more notches having a T- shaped orbayonet outline and adapted to engage one or more bar-retaining ringswhile said bar is also provided in said radially inner surface with aprojection extending laterally beyond the connection-carrying collar andadapted to be engaged outwardly by a retaining ring of a larger diameterthan the first mentioned rings, the bar being provided finally at itsend facing away from said collar with a notch formed endwise and adaptedto engage a further bar-retaining ringj Thus, the difference in diameterbetween the outer ring engaging the lateral projection and the nearestof the firstmentioned rings at a point in registry with theconnectioncarrying collar allows maintaining a large cross-section forthe retaining lugs formed on the bar between the notches formed in it inthe area which is subjected to the maximum tearing out stresses andwherein the bars are held in position b a double engagement withretaining rings,

In an advantageous embodiment, the notch formed endwise in each bar onthe side facing away from the collar is given the same outline as theprojection provided on the side facing the collar. I obtain thus asubstantial economy in metal since the metal obtained by the cutting outof the endwise notch in one bar may form the projection of a barproduced in immediate sequence.

The electrical insulation of the bars with reference to the metal ringsis ensured by molded or injected insulated material introduced after therings have been precedingly centered by means of insulating platesfitted between the bars and of which the outlines project beyond theoutlines of the bars into the notches of the latter adapted to engagethe retaining rings.

In order to obtain a good electrical insulation between the bars and therings, the notches adapted to house the rings are given a large sizewith reference to the crosssection of the rings. Consequently themaximum crosssection of the retaining lugs cut out of the bars betweenthe notches is very limited, which limits all the more the maximumrotary speed allowed for operation of the motor or the like machine.

In a particularly advantageous embodiment, the barretaining rings aremade of an insulating material having a large mechanical resistance,such as a mass of glass fibres embedded in synthetic resin.

Thus, not only is it possible to reduce the size of the notches providedfor the housing of the rings since the contact between the rings and thebars has no electrical action, but furthermore the problem of centeringand holding in position the rings before injecting insulating materialis avoided, said rings forming in fact binding hoops.

Preferably, the shoulder constituted by the outer ring engaging thelateral flange or its bed of insulating material is flush with thebottom of the central notches and serves as a support for the externalconnecting bars which may consequently be clamped in position by anouter hoop Without any risk of deformation.

My invention will be clearly understood from a reading of the followingdescription, reference being made to the accompanying diagrammaticdrawing illustrating by way of example and by no means in a limitingsense two embodiments of a commutator incorporating my improvedarrangement. In said drawing:

FIG. 1 is a perspective view of a first embodiment of said commutator.

FIG. 2 is a plan view of a bar of the commutator according to FIG. 1.

FIG. 3 is a part sectional view extending axially through line 33 ofFIG. 1.

FIG. 4 is a perspective view of a second embodiment of said commutator.

FIG. 5 is a part sectional view along the axis of the commutatorillustrated in FIG. 4.

The commutator illustrated in FIGS. 1 to 3 is constituted in aconventional manner by bars 2 fitted around a central sleeve 12 whileinsulating plates 3 are fitted between the bars.

The bars 2 are assembled in the example illustrated by three metal rings4, 5 and 6 (FIG. 3).

FIG. 2 shows the outline of a bar 2 along the inner surface of which areformed two notches 7 and 8 and a lateral projection 9 adapted tocooperate with the rings 4, 5 and 6 respectively so that the latter maybe held in their assembled position.

The central notch 8 is given the shape of a bayonet slot and serves forhousing the ring 5, the opening of said bayonet slot facing away fromthe radial outer extension 2a at one end of the bar 2, which extensionis adapted to form part of a collar 11 holding in position theconnections with the convolutions of the rotor windings.

The lateral projection 9 is provided at the end of the bar 2 located onthe same side as said extension 2a, said projection 9 being adapted toform part of an annular shoulder over which is fitted outwardly the ring6 of which the bore is larger than that of the other rings 4 and 5.

The outer notch 7 is provided at the end of the blade 2 facing away fromthe projection 9. It is adapted to engage the retaining ring 4. Theoutline of said notch 7 is advantageously the same as that of theprojection 9 so that the cutting of a projection 9 in one bar may formthe notch 7 in another bar cut out of a same blank; this provides theadvantage of a substantial economy in the metal out of which the bars 2are cut.

In order to prevent any contact between the bars 2 of the commutator andthe rings 4, 5 and 6, the latter are held fast at a distance from theedges of the notches in which they are housed before the injection ormolding of an insulating material adapted to secure them finally inposition.

During said injection, the setting in position and the centering of therings 4, 5 and 6 are advantageously ensured as well-known in the art byportions of the insulating plates 3 projecting beyond the outlines ofthe bars 2 into the notches 7 and 8 thereof and around the projections 9as clearly shown in interrupted lines in FIG. 3.

As also clearly shown in said FIG. 3, the end of each bar 2 carrying theextension 2a, which end is subjected to the highest centrifugal forcesand consequently to the highest stresses is held in position by therings 5 and 6, without the presence of the latter leading to anyreduction in the cross-section of the inner section 13 of the bar 2,which section 13 serves for anchoring purposes and must therefore resistefiiciently centrifugal force.

This is ascribable to the fact that the ring 5 is fitted inside thenotch 8 while the ring 6 is fitted outside the projection 9 andfurthermore the bore of said ring 6 is clearly larger than that of thering 5.

In the example illustrated in FIGS. 4 and 5, the system of bars 14,between any two successive bars of which is inserted an insulating plate15, is assembled by means of rings 16, 17, 18 and 19 made of insulatingmaterial with sufiicient mechanical properties, as is the case forinstance for glass fibres embedded in synthetic resin.

The use of such rings has the advantage that their contact with the bars14 has no detrimental electric effect.

In said embodiment illustrated in FIGS. 4 and 5, the central rings 17and 18 are housed in radially inner central notches 21 and 22 having aT-shaped outline. The

outer ring 16 is housed inside a notch 23 formed endwise in the bars 14at the end thereof facing away from their radial extension 14a adaptedto carry the electrical connections of the rotor and lastly the ring 19is fitted with a force fit around the projections 24 provided at theends of the bars carrying the extensions 14a.

The arrangement is secured in a conventional manner by means of aninsulating material 25 introduced through injection or molded andrigidlysecuring the commutator coaxially over the sleeve 26.

The assembly of such a commutator is a very easy matter when comparedwith the assembly of commutators of a known type wherein the retainingrings are made of metal. As a matter of fact, no special care is to betaken when fitting the rings in position to hold them away from the barsand, in contradistinction they may be fitted with .4 a force fit overthe projections or into the notches of the bars.

A further advantage in the use of such rings consists in that thenotches may be given a size which matches exactly the cross-section ofthe rings and, consequently, the cross-section of the retaining lugsformed in the bars between their notches may be increased.

Obviously, my invention is by no means limited to the embodiments of acommutator which have been described hereinabove by way of example andin a non-limiting sense and it covers in contradistinction all themodifications thereof falling within the scope of the accompanyingclaims. In particular, the number and the outline of the notches 8 (or21 and 22) provided between the notches 7 (or 23) and the lateralprojections 9 (or 24) are irrelevant, said number being obviously afunction of the length of the commutator and furthermore the outline ofthe cross-section of the retaining rings and the nature of the materialor materials forming them may be chosen as desired.

What I claim is:

1. In a commutator for rotary electrical machines, the provision of aplurality of similar radially distributed conductive elongated bars eachhaving an inner edge with at least one notch extending at least at oneend within the body of the bar to form a tongue therein along said edge,each bar having opposite ends and including at one end, and in itsplane, a radial outwardly directed extension and a lateral projection,each bar being provided at its other end with a further notch extendinginto the transverse edge of the bar, radially distribtuted insulatingplates separating successive bars and rings fitted in correspondingnotches of the different bars and extending around the lateralprojections on the different bars, the lateral projection of each barhaving an outline matching the outline of said further notch therein andbeing disposed at the same level thereof in said bar.

2. A commutator as claimed in claim 1 comprising a sleeve supportingsaid bars and plates, and an insulat ing body secured to said sleeve andfilling said notches and enclosing said projections of said bars, saidrings being embedded in said insulating body.

3. A commutator as claimed in claim 1 wherein the rings are made of aninsulating material having relatively high mechanical strength.

4. A commuttor as claimed in claim 1 wherein the rings are made of glassfibres embedded in synthetic resin.

5. A commutator as claimed in claim 1 wherein the outer surfaces of thelateral projections on the bars are substantially flush with the bottomsurfaces of the first mentioned notches and are adapted to carryconnecting bars.

6. A commutator as claimed in claim 4 wherein said rings are in directcontact with said bars.

References Cited UNITED STATES PATENTS 2,565,120 8/1951 Carter et al310-236 2,600,312 6/1952 Meier 310236 3,290,527 12/ 1966 Habermann 3l0-235 3,079,520 2/1963 Schafer et al 310-235 FOREIGN PATENTS 853,60810/1952 Germany.

WARREN R. RAY, Primary Examiner.

R. SKUDY, Assistant Examiner.

